Abstract:The influence of rare-earth(RE) oxide additions, e. g. Y₂O₃ and Gd₂O₃ on the hot corrosion behaviors of the NiAl coatings exposed to the Na₂SO₄+25wt.- % K₂SO₄ fused salt at 850℃ was studied. The experimental results show that the RE oxide additions can not only reduce the corrosion rates of the coatings, but also lighten the corrosion degree of the sulfides on the coatings through the formation of stable RE-oxygen-sulfides which are aggregated in the surface corrosion areas of the coatings. With increasing additions , the effect of the RE oxides against hot corrosion will improve. Furthermore, the corrosion form of the sulfides will change from imhomogeous corrosion , in which case the intracrystalline local corrosion is predominant , to mixed type corrosion ,in which case the transgranular corrosion is predominant.

Key words: rare earth oxides NiAl based coatings hot corrosion